1. Field of Invention
The present invention is directed to an insulator for an electrical connector having air cavities between contact cavities to reduce the effective dielectric constant of the material used to construct the insulator, which allows for a tighter contact pitch.
2. Description of Related Art
Prior connectors have featured air channels or passages. Connectors with air channels or passages are mentioned, for example, in U.S. Pat. No. 6,814,590; U.S. Pat. No. 7,303,427; U.S. 2007/0293084; and U.S. 2010/0330846. In contrast to the air cavities of the present invention, however, the air channels or passages in other connectors perform a completely different function. In these other connectors, the connector contacts are intended to carry a high current, not high-speed digital data. In connectors that carry a high current, the purpose of the air channels is to allow airflow within the connector for the purposes of dissipating the heat that is generated by the high current flowing through the resistance of the contacts. This heating is commonly referred to as “I2R” heating because the power generated in the contact is equal to the current squared times the resistance of the contact. In many such connectors, the characteristic impedance between adjacent contacts is not a design consideration at all.
While other connectors have used air cavities, those applications were primarily directed to high-current connectors that needed the air cavities to dissipate heat. In other applications concerning power distribution systems, a higher effective dielectric constant is desirable to reduce impedance to minimize voltage drops. In some traditional applications, reducing impedance and increasing the relative dielectric constant is a design consideration for the following reason. If the power contacts are intended to supply DC power to integrated circuits (“IC”) that are switching high currents at high speeds, which is common in large ICs with lots of gates such as microprocessors and gate arrays, then the impedance of the power supply circuit can be important because the power supply system must be able to supply nearly instantaneous surges of current to feed the fast-switching gates of the ICs in which many gates may be required to switch at the same time. In such cases, even though a single gate may switch only 5 mA (for example), the total current demand for 1,000 gates that switch simultaneously would be 5 amps. Since it is desirable to have a very low voltage drop between the power source and the IC, the impedance of the power circuit must be very low. Even if the impedance of the power supply circuit were only 0.10 ohms, the voltage drop in this example would be 0.5 volts (5 amps times 0.1 ohm), which would be totally unacceptable in most applications. Thus, in designing power distribution systems for high speed digital data applications (printed circuit boards, cables, and connectors for example), it is desirable to make the characteristic impedance between the power line and its return path as low as possible in order to minimize the voltage drop. Making the impedance as low as possible requires using an insulating material with as high a relative dielectric constant as possible.